When you buy a coral frag, it is a baby and it will grow. You can take of the stick off the coral plug with pliers (don't leave the coral too long out of water, I try not to exceed like 1-2 mins). You can keep the disc wih the coral and glue it on your rock. The baby coral will grow and overgrow the disc. Also corraline algea will cover it soon, so the disc will soon disappear.